As semiconductor technologies continue to develop, the polysilicon gate electrode layer has been replaced with a metal gate electrode layer. Compared with a polysilicon gate electrode layer, the metal gate electrode layer has lower gate resistance, eliminates the polysilicon depletion effect, and has a good compatibility with high-K gate dielectric materials.
To meet the requirements of high-performance devices, a single-layer or multi-layer of work function layer needs to be formed between the metal gate electrode layer and the gate dielectric layer. The work function layer is used to adjust the threshold voltage of an NMOS transistor or a PMOS transistor. A dielectric barrier layer needs to be formed between the gate dielectric layer and the work function layer, and the dielectric barrier layer is used to block the diffusion of the atoms in the gate dielectric layer into the work function layer. Also, a gate barrier layer needs to be formed between the metal gate electrode layer and the work function layer, and the gate barrier layer is used to block the diffusion of the atoms in the metal gate electrode layer into the work function layer.
However, the performance of conventionally-formed dielectric barrier layer and the gate barrier layer still needs to be improved. The disclosed semiconductor structure and fabrication method are directed to solve one or more problems set forth above and other problems in the art.